Apparatus for plasma treatment of golf balls

ABSTRACT

The present invention relates to an improved apparatus for plasma treatment of golf ball surface. The improved apparatus comprises a cylindrical basket shaped rotating tumbler made from aluminum sheet metal that holds a plurality of golf balls within a sealed casing for surface preparation. A staggered hole pattern yields about 57% of open area in the tumbler surface to insure evacuation with minimum resistance. The holes are individually machined and have machined radiuses at each side of the sheet metal to allow for adequate coverage of a hard anodic coating which is necessary for protection of the sheet metal from the high intensity plasma.

FIELD OF THE INVENTION

The invention relates to an improvement in the apparatus for treatingthe surface of golf balls with unpolymerizable gas plasma. Morespecifically, the improvement is a rotating tumbler.

FIELD OF THE INVENTION

Conventional golf balls can be divided into two general types or groups:solid balls and wound balls. The difference in play characteristicsresulting from these different types of construction can be quitesignificant.

Balls having a solid construction are generally most popular with theaverage recreational golfer because they provide a very durable ballwhile also providing maximum distance. Solid balls are generally madewith a single solid core, usually made of cross-linked rubber, which isencased by a cover material. Typically the solid core is made ofpolybutadiene which is chemically cross-linked with zinc diacrylicand/or similar cross-linking agents and is covered by a tough, cut-proofblended cover. The cover is generally a material such as SURLYN®, whichis a trademark for an ionomer resin produced by DuPont. Wound ballstypically have either a solid rubber or liquid center core around whichmany yards of stretched elastic such as Balata or polyurethane arewound. Wound balls are generally softer and provide more spin, whichenables a skilled golfer to have control over the ball's flight andfinal position.

Regardless of the form of the ball, players generally seek a golf ballthat delivers the best combination as to maximum distance, spin anddurability. Golf ball manufacturers are continually searching for newways in which to provide golf balls that deliver the maximum performancefor golfers at all skill levels.

The outer cover of either type golf ball are formed with variousmaterials that may be thermoplastic urethane elastomers, Balata,ionomers (which are metallic salts of copolymer of ethylene and an acidprecursor), Surlyn® blends or any other appropriate materials. The coversurfaces are formed with dimples of various numbers, sizes and patterns,which improve flight distance, control and stability. The outer surfaceof the ball covers usually have the manufacturers indicia disposedthereon as well as an application of a paint or clear lacquer for thepurposes not only of good appearance but also of improving fightdistance and protecting of the indicia imprinted thereon.

The coatings are often subject to exfoliation due to strong impact witha golf club, which not only can mar the appearance of the ball, but canadversely affect the distance and stability of the ball flight. Thisexfoliation can be reduced by improved adhesion techniques between golfball cover surface and coating.

In order to improve adhesive bonding between the outer surface of thecover and the applied coating, many methods have been tried andadministered. One process is the flame method. Used with golf balls thishas presented a problem because of the heat generated, which can scorchthe ball or cause burns to the inner polymer materials. Sand blasting isanother technique for roughing up the ball, but again, this can beunsatisfactory in that precisely designed and formed dimples can bedamaged. One method that has helped reduce product defects of the abovenature involves treating the organic cover material of the golf ballwith glow discharge plasma of unpolymerizable inorganic gas toadvantageously modify the surface of the cover. A coating is thenapplied in an apparatus adapted to expose the all over surface of theball to the plasma. The so-called glow plasma can be generated byapplying high voltage to the gas at a low temperature of about 20° C.under a low pressure in the range of 100-200 mm Torr, more preferably200 mm Torr. Such a method is described in U.S. Pat. No. 4,613,403issued to Oyachi et al.

The glow discharge plasma method for treating golf balls requires theuse of an apparatus that incorporates a rotating tumbler thatsimultaneously contains and moves a plurality of golf balls while theyare being subjected to the glow discharge.

A significant problem is inherent in the make-up of conventionaltumblers. Tumblers must be rigid to withstand handling thousands of golfballs per batch. They also should be designed to promote an evendistribution of plasma discharge generated at about 13.56 MHz and 1200Watts. They must allow a fast pump-down time for production efficiency.They must rotationally tumble golf balls without marking or marring themwhile constantly exposing the ball surfaces. A major problem with priorart tumblers is that the plurality of holes in the surfaces of thesetumblers are created by a shearing process which results in holes havingsharp edges on each side of sheet. The size of the holes is also ofgreat importance as holes that are too small may severely stall theevacuation process. And holes that are too large may allow the surfaceof the ball to become lodged therein, whereby the ball will not movefreely and thereby not receive an even coat of plasma. The holesthemselves are subject to the high intensity plasma and holes that aremade by the shearing method may have sharp ridges. Hole geometry of thistype makes it very difficult to apply the proper anodic protectivecoating, and in time the plasma will erode the unprotected hole and itsedges causing pitting, nicks, and other irregularities. Golf ballscontacting these problem areas will be subject to marking and otherpotential product defects. The present invention describes an apparatusthat dramatically reduces, if not totally eliminates, product damagecaused by these type of tumblers.

SUMMARY OF THE INVENTION

The present invention is directed to an improved rotating tumbler forholding golf balls during a treatment with glow discharge plasma of highintensity. The plasma is applied under conditions of low pressure ofabout 100 to 200 mm Torr and high voltage (13.56 MHz with an output ofabout 1200 Watts). The improved apparatus utilizes a hole pattern thatgives the tumbler improved stability. This hole design that will allow aprotective hard anodic coating to be applied at the hole edges so thatball marking and defects will be minimized. And properly sized holeswill allow for speedy evacuation and more stable tuning frequency.

An embodiment of the invention is a tumbler utilizing a cylinder ofaluminum sheet metal having a plurality of individually machined holesin a staggered pattern, one end of the cylinder being enclosed with agenerally circular sheet of aluminum that also includes a staggered holepattern. The other end of the cylinder remains open for thetransportation of golf balls into and out of the tumbler. The pattern ofholes is designed to generate stability during the tumbling operation.

The tumbler of the present invention is hard anodic coated forprotection against the rigors of the plasma process. Each hole furtherhaving a radius machined about the outer ridges of the holes tofacilitate the application of the anodic coating at these locations andto remove any sharp edges that may mark or defect the golf balls.

The present invention is also directed towards having the size of theholes of specific diameter. The diameters of the holes should be between0.25 inches and 0.50 inches, and more preferably about 0.375 inches,with the radius at the hole edges about 0.09 inches. The holes should belarge enough to allow for a quick evacuation with minimal resistance,but not so large that they will nestle with the ball thereby preventingan even coating of plasma to the ball surface. The number and allocationof holes should be such that more than 50% of the tumbler surface isopen surface. The pattern of holes of the invention which is generally0.375 inch holes on a staggered line of 0.75 inches provides for about57% of open surface area which produces an evacuation time of less than60 seconds.

The interior of the holes are also subject to the high intensity plasmaand as such can possibly create an unstable process that requiresfrequent tuning of the radio frequency. The size and design of the holesof the present invention promotes a stable process with only infrequenttuning required.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a pictorial view showing a surface-treating plasma barrelreactor used in the present invention.

FIG. 2 is an elevational sectional side view of FIG. 1

FIG. 3 is an elevational sectional view of the casing of FIGS. 1 and 2specifically detailing the rod member.

FIG. 4 is a partial longitudinal sectional view of the tumbler portionshowing the hole pattern and arrangement.

FIG. 5 is an elevational end view of FIG. 3.

FIG. 6 is a cutout view of on of the holes in the tumbler.

FIG. 7 is a schematic diagram of the surface-treating apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, there is shown a known plasma barrel reactor 10.FIG. 2 illustrates a reactor 10 having a generally barrel-like,cylindrical casing 11 with a generic internal tumbler 12 that is adaptedto receive a plurality of articles, preferably golf balls 13. Thereactor 10 is equipped with conventional means for supplying power,gases, etc., for which a schematic is shown in FIG. 6 and discussed indetail below. FIG. 3 shows tumbler 12 including a plasma generation rod17 and chamber 19 for holding golf balls (not shown). In the tumbler 12golf balls are subjected to being surface-treated by a gas plasmaprocess. This treatment is a necessary step in the preparation of thegolf ball surface for an application that may comprise either a coat ofpaint or clear lacquer. Tumbler 12 is caused to rotate within the sealedcasing 11 thereby constantly keeping golf balls in motion so that theymay all receive an even distribution of plasma discharge upon theirsurfaces.

FIG. 7 is a schematic layout of reactor 10 showing a plurality of portsfor introducing and exhausting the working gases, and the location ofgolf balls 13 within the tumbler 12. Valve means 14 provides forin-letting of gases into and out of the casing 11, so as to maintain adesired volume of gas therein. A valve means 15 is arranged in a line tobe led to a pump, not shown, for decreasing pressure in the casing 11. Avacuum gauge 16, tumbler 12 for holding the golf balls 13 therein, aglow discharge plasma rod 17, and an electric source 18 make up theremaining working components of the apparatus.

The method for treating golf balls 13 with glow discharge plasma isdescribed in U.S. Pat. No. 4,613,403, issued to Oyachi et al., which isincorporated in its entirety herein. The covers of the balls 13 areusually made of various materials that may be thermoplastic urethaneelastomers, Balata, ionomers, Surlyn® blends or any appropriatematerials. The outer cover surface of the balls 13 is usually coatedwith a paint or clear lacquer, not only for the purposes of improvingflight distance and stability of ball flight, but also for goodappearance. In order to improve the adhesive bonding between outersurface of the ball cover and the coating, the golf ball 13 is treatedwith unpolymerizable gas plasma prior to coating. The glow dischargeplasma can be generated by applying high voltage from source 18 to thegas provided from a gas source through valve 14 at a low temperature ofabout 20° C. and under a low pressure in the range of 100-200 mm Torr,more preferably 200 mm Torr. The unpolymerizable inorganic gas usedherein is preferably oxygen.

EXAMPLE

A plurality of balls 13 are held in the tumbler 12 and air is dischargedby actuation of the pressure reduction valve 15, so as to make thepressure about 0.002 Torr. Then the inorganic gas is supplied into thecasing 11 by actuating the valve 14 in order that the pressure istherein increased to be about 100 Torr. The tumbler 12 is rotated undera high frequency voltage from source 18 of about 10 to 15 MHz with anoutput in the range of about 900 to 1500 Watts being applied acrosselectrodes. The electrodes consist of a plasma rod 17, which islongitudinally centered in the middle of the tumbler, and the casing 11.Golf balls 13 are therein treated with inorganic gas plasma for arelatively short period of time preferably between 6 to 10 minutes untilevery ball is coated with plasma discharge.

The present invention, as shown in FIGS. 4 and 5, provides for animprovement in the apparatus for carrying out the above procedure. Thetumbler 12 must be rigid, and allow for the balls 13 to roll free.However, it must also provide a chamber environment that preventsmarring or marking of the golf ball 13.

A standard perforated aluminum sheet 20 with a pattern of holes 21 isformed into a cylindrical basket. This pattern of holes 21 is preferablynot created by means of a shearing process, which results in holes thatcontain sharp edges on each side of the sheet, but rather each hole 21is individually machined. A plurality of ribs 27, longitudinallydisposed, provide structural integrity to the tumbler 12 and forincreased agitation of golf balls 13. The interior surface 22 andexterior surface 23 of the tumbler 12 are sandblasted and hand polishedto remove any rough edges. The ribs 27 are perpendicular to the tumbler12 and are about 0.5 to 2 inches in depth. Holes 21 each have a throughopen diameter (D) between about 0.25 inches to about 0.50 inches,preferably about 0.375 inches of through opening. Holes 21 arepositioned for maximum workable open area and as such holes 21 of 0.375inches diameter are machined on a staggered pattern (P) of about 0.75inches. The pattern is selected so as to yield about 57% open surfacearea in tumbler 12, which allows for quick evacuation (less than about60 seconds) with minimal resistance. One embodiment of the invention hasa tumbler capacity of 1200 golf balls 13 which requires improved tumblerdesign to insure that each ball 13 receives an even and adequateexposure of glow plasma discharge. The tumbler 12, as are holes 21, aresubjected to high intensity plasma, and for protection the tumbler 12 ishard coat anodized with about 0.003 inches applied for abrasionresistance (per mil spec. MIL-A8625F Class III). The aluminum sheet 20has a thickness (T) of about 0.250 inches to about 0.375 inches thickand, as previously stated, fabricated with a pattern of holes around thecircumference and rear face 25 to the cylinder. The front face 26 of thecylinder is open to allow for product transport to and from the tumbler12.

During the process in which the anodic protective coating is applied,the relatively rounded edges of the holes 21 assist in providing an evenapplication of the coating and also an adequate thickness. When theplasma generator is activated, high intensity plasma is generated withineach hole 21. The effect of the plasma within the hole 21 would causeeroding of aluminum metal which has not been adequately protected by ahard anodic coating. This could result in a burnt effect at the edge ofthe hole 21. The surface of the golf ball 13 making contact with theedges of the eroded holes edge causes substantial contamination andmarking of the ball 13. Thus rounding of edges is important, preferablyedges have a radius of between 0.06 inches and 0.12 inches and morepreferably about 0.09 inches.

The size of the openings of the hole 21, in addition to their functionto provide quick evacuation time, is also important for maintaining aconsistency in radio frequency tuning. The presence of high intensityplasma within the holes 21 can create an unstable process thatnecessitates frequent tuning. This situation is accentuated by the sizeof the hole. The smaller the hole the greater the instability andtherefore more tuning.

An embodiment of the invention provides protection against eroding ofthe hole 21 edges by machining each hole, on interior and exteriorsurfaces, to a diameter of about 0.375 inches with a radius (R) of about0.09 inches as shown in FIG. 6. This inherently removes any sharp edgesand presents an adequate surface area on the ridges of the holes 21 toallow a protective anodic coating to be applied. The coatingsubsequently protects against erosion at the ridges of the holes 21which is the principal reason for ball marking and other defects duringthe process.

The pattern of holes geometry is such that the holes are in a staggeredarrangement and measure 0.75 inches apart from each other based on ameasurement from the center of any one hole to the center of an adjacenthole. By the employment of this specific pattern of hole geometry to thetumbler 12, the present invention improves upon known tumblers and meetsseveral objectives. First it provides an apparatus that will improveevacuation times. It then will reduce radio frequency tuning.Efficiently apply an even coat of glow plasma discharge. Next, reduceoverall equipment maintenance. And finally, reduce, if not eliminate,product marking and defects.

While it is apparent that the illustrative embodiments of the inventionherein disclosed fulfill the objectives stated above, it will beappreciated that numerous modifications and other embodiments may bedevised by those skilled in the art. Therefore, it will be understoodthat the appended claims are intended to cover all such modificationsand embodiments which come within the spirit and scope of the presentinvention.

1. An apparatus for treating golf ball surface comprising a sealedcasing, a tumbler for holding golf balls in the casing, and an electricsource for applying high voltage across the electrodes in order togenerate glow discharge, wherein the improvement comprises the tumblerfurther having: a plurality of perforated holes in a staggered patterncovering a substantial portion of the tumbler surface; and the pluralityof perforated holes have a curved radius machined about their outeredges, wherein the curved radius is about 0.06 to 0.12 inch.
 2. Anapparatus for treating golf ball surface comprising a sealed casing, atumbler for holding golf balls in the casing, and an electric source forapplying high voltage across the electrodes in order to generate glowdischarge, wherein the improvement comprises the tumbler further having:a plurality of perforated holes in a staggered pattern covering asubstantial portion of the tumbler surface; and the plurality ofperforated holes have a curved radius machined about their outer edges,wherein the plurality of holes have a through diameter greater thanabout 0.25 inch and less than about 0.50 inch.
 3. An apparatus fortreating golf ball surface comprising a sealed casing, a tumbler forholding golf balls in the casing, and an electric source for applyinghigh voltage across the electrodes in order to generate glow discharge,wherein the improvement comprises the tumbler further having: aplurality of perforated holes in a staggered pattern covering asubstantial portion of the tumbler surface; and the plurality ofperforated holes have a curved radius machined about their outer edges,wherein the staggered pattern includes through-holes of about 0.375 inchdiameter on a 0.750 inch staggered pattern.